Question 188294
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Basic Eqn, <font color=blue>Speed=Distance/Time</font>


We get, Distance=Speed*Time


Since two cars travel on the same highway 420 miles apart, we need to add the Speed of each in 4 hours to cover the 420 miles.


Let {{{S[1]=15+x}}}, and  {{{S[2]=x}}}



{{{Distance=S[1]*T[1]+S[2]*T[2]}}}
{{{420mi=(15+x)(4)+x(4)}}}
{{{420=60+4x+4x}}}
{{{420-60=8x}}}
{{{360=8x}}} ------>{{{cross(360)45/cross(8)=cross(8)x/cross(8)}}}
{{{highlight(x=45mph)}}}, Speed of Slower car
{{{45+15=highlight(60mph)}}}, Speed of Faster car


Thank you,
Jojo</font>